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I don't believe that the XP-72 was ever intended to carry a turbocharger.
The compressor driven by the extension shaft was the first stage of a two stage system - the engine retaining its integral supercharger.
If the XP-72 ran without the first stage supercharger then it is possible that the engine supercharger was rated for the XP-72's maximum speed altitude.
The XP-72 was heavily based on the P-47 with its rear fuselage mounted CH-series turbocharger. The reasoning behind the auxiliary (or first stage) supercharger being mounted in the rear fuselage and driven by an extension shaft was to maintain weight balance. I suspect, therefore, taht the auxliary supercharger was fitted, even if it wasn't operational.
As a check on some of the performance figures for the XP-72 we can look at the P-47M. The P-47M was supposed to do 367mph at sea level using 2800hp. using the cube law to figure the power needed for 480 mph it comes out to just over 6100hp. even with 3500hp the XP-72 is going to need a LOT of drag reduction to get to 480mph at sea level.
The P-47M was supposed to do 473mph at 32,000ft using 2800hp and have an "operating speed" of 360mph on 1270hp (75% of 'rated power'="max continuous")at 32,000ft.
This makes sense although it goes counter to the P-47 trend with its turbo.
So any Ta 152/Fw190D with DB 603N or Jumo 213J/S (the S version being specialized for low altitude performance) offering about 2700/2800 PS would be on par with the F8F-2 with its 2800PS engine (Bill Gunston).
The Jumo 213A made 1,750 PS (2100 PS with MW50) and was used in the early D's. The Fw-190D-9 started out with no MW50, but Fw increased the manifold pressure to allow 1,900 PS, effective to 16,400 feet, which is about the useful ceiling of the P-39, so the extra 150 PS was not useful to the D-9 at all. MW50 power for the retrofitted units was still 2,100 PS.
The early D's lacked the high turn rate and high roll rate of the radial-powered cousins. Many D-9's were not equipped with MW50 and their acceleration and top speed fell short of Allied fighters at low altitude. The D-9 was an effective medium-altitude, high=speed fighter but its performance fell off above 20,000 feet.
How would the Ju-213 do with 130 fuel.
How would the Ju-213 do with 130 fuel.
The early D's lacked the high turn rate and high roll rate of the radial-powered cousins. Many D-9's were not equipped with MW50 and their acceleration and top speed fell short of Allied fighters at low altitude. The D-9 was an effective medium-altitude, high=speed fighter but its performance fell off above 20,000 feet.
Which Bearcat flew at 2800 hp?
Oh, about the Fw 190D-9's falling off above 20,000 feet, that's true. The early models didn't have MW50 or GM1 and did fall off about there. Later, they were improved and flew well up into the mid 30's. They also didn't turn (read picth) as well as their BMW 801 radial-powered cousins. It is a matter of moment of inertia with the liquid-cooled V-12 sticking out much farther from the firewall than the BMW radial. Once the liquid cooled versions of the Fw 190 / Ta 152 acquired more wingspan, they didn't roll nearly as well as the A/F series either.
But I don't credit it with perfromance beyond it's capability.